The invention relates to an endoscopic instrument which at the distal end region of an elongate shank comprises two working parts of which at least one is pivotingly movable relative to the other, and at the proximal end region of the shank is provided with a handle for actuating at least one of the working parts via an actuation rod running in the shank, wherein the working parts in the region of the pivoting mounting are submitted to a spring force for pressing apart these parts.
Such an endoscopic instrument is described in EP-0 537 574 A2. It may be formed for example as a pair of scissors blades wherein the one of the blades or cutting parts is mounted in a pivotingly movable manner by way of an axle pin, while the other blade or cutting part is stationary. So that all blade or cutting parts acting as working parts during the complete cutting procedure remain in firm contact with one another over their whole working length, that is to say are pressed on one another, a disk spring or plate spring is mounted on the axle pin outside the working parts, with whose force the two working parts are pressed onto one another. With this instrument there is the disadvantage that the pressing force of the spring acting on the two working parts can only be set roughly and with difficulty since the calculated dimensions for the axle pin and the pressing spring on account of the manufacturing and assembly tolerances for these parts with which tissue of a patient is to be gripped and/or cut, after their assembly, mostly have not led to the desirable value of the required pressing force for the working parts. Thus the endoscopic instrument cannot be applied to the same degree to soft or harder tissue, for example cartilage tissue. If the result of the assembly is a relatively strong pressing force then the instrument is not suitable for cutting soft tissue since it may not be delicately handled, and vice versa. A further considerable disadvantage with the prior known instrument lies in the fact that it only has a slight safety against overloading which is determined by the height, which cannot be changed, of the plate spring which is pretensioned in the assembled condition and is seated on the axle pin. By way of this the working parts, on cutting the thick and gristly tissue of a patient, may only give slighly along the axle pin. Therefore, in particular with an instrument with a low pressing force of the working parts onto one another there exists the extremely premature danger of the instrument, with overloading at least in the region of the cutters of the working parts, being damaged by the bending of these parts. Furthermore with the known instrument it is disadvantageous that the assembly of the working parts by way of an axle or linkage pin and a plate spring or spring disk by way of a rivetting procedure is relatively time consuming and complicated in manufacture with the associated manufacturing costs.